Daylight Illuminance Research Articles

Investigating the interrelation of influential parameters on indoor daylight quality using structural equation modeling

Daylight quality in office spaces is an essential parameter that affects indoor environmental quality and significantly reduces energy consumption. Several individual, environmental, and physical parameters influence the visual perception of occupants. Therefore, visual comfort is a result of the combination and interconnection of all these factors. This study aims to evaluate and prioritize the factors that have a significant impact on indoor daylight quality, by using post-occupancy evaluation to examine how different variables affect human visual comfort by taking into account the simultaneous and interactive effects of these variables. A new modeling framework is constructed through partial least squares structural equation modeling (PLS-SEM) to evaluate the relationships among variables. The proposed model has 57.6% explanatory power for occupants' satisfaction with the lighting environment with R2 = 0.576. Additionally, analysis of the data using the Importance-Performance Map (IPMA) reveals the priority of relevant factors. According to the findings, among the 17 variables studied, horizontal and vertical daylight illuminance, glare sensation, distance from the window, and thermal satisfaction have the greatest impact on visual perception, in that order. Although the other factors studied are still important, in comparison with these factors, have less impact on the assessment visual comfort. Therefore, to improve the quality of office spaces with daylight and increase occupants' satisfaction, the focus should be on enhancing these five factors first.

Simulating Energy Performance and Illustration through Passive Techniques: Case of Institutional Buildings in Ahmedabad, Gujrat, India

The research examines the passive techniques: courtyard and WWR of institutional buildings of Gujrat. The report is a component of a comprehensive research project that aims to investigate how architectural factors affect how efficiently and environmentally sound classrooms work in hot and dry areas. The parametric analysis of the impact of two various courtyard designs on daylighting in Ahmedabad's typical hot and dry environment is shown here. The methodology was based on simulations created by the computer programs Ecotect and Revit-Insight. Two case studies with two different sky conditions were examined. The models have revealed variations in the illuminance level of daylight under overcast and clear sky circumstances. For instance, the first case has a higher WWR than the second, hence the results indicate a roughly 18% increase in the level of daylight illumination in the first case compared to the second. According to the results, it is possible to rely mostly on daylighting to provide appropriate lighting in classrooms.

Parametric model of window-integrated planer Cassegrain concentrator-based shading system (PCSS)

This study proposes a performance-driven design method for a new and novel, window-integrated planer Cassegrain concentrator shading system (PCSS) for daylight and energy applications. The integration process is complex and needs to address multi-disciplinary concerns, where the PCSS’s performance depends on system design and building geometries ensuring good solar gains. The method is rigorous yet adaptable to inform decision-making involving multiple stakeholders and promote the use of PCSSs as, window-integrated technology. The method contributes to engineering PCSS with respect to windows in a parametric model. A total of 3,750 designs are generated by controlling parameters related to the building (i.e., orientation, window-to-wall ratio (WWR), louvers’ tilt and number), and PCSS (i.e., modules number, mirrors’ shape and dimensions). The method is validated in an illustrative case study of a residential building in Madrid (Spain), where the performance is assessed in terms of annually-averaged electrical load match index (av.LMIEl), thermal load match index (av.LMITh), continuous daylight autonomy (cDA(500 lx)), and useful daylight illuminance (UDI(100–2000 lx)). Further, a sensitivity analysis is performed to investigate the relative significance of parameters. The method enables a performance-driven design of buildings and PCSSs and facilitates stakeholders for informed decision-making in projects concerning energy transition in buildings.

Impact of Window Design on Dynamic Daylight Performance in an Office Building in Iran

Window design affects the building's appearance. Besides, it has a significant impact on daylight performance and the visual comfort of interior spaces. Therefore, choosing the shape and position of windows can be a challenge for architects. This research aims to investigate the impact of window design on dynamic daylight performance to enhance visual comfort. The research examines five common window shapes that are located in two different positions on the southern-facing side. The most common dynamic daylight metrics of LEED v4.1 were used to investigate the spatial daylight autonomy (sDA), and annual sunlight exposure (ASE). Furthermore, useful daylight illuminance (UDI) was considered a complementary approach to assess useful daylight levels. The metrics are examined in three cities including Mashhad, Isfahan, and Bandar Abbas, which are located in the northeast, center, and south of Iran, respectively. Thirty simulations in each city are conducted by Grasshopper Graphical editor as a parametric interface and its plugins, ladybug, and honeybee for dynamic daylight analysis. The results emphasize that window design has a significant impact on dynamic daylight performance. The square window meets the LEED needs in three cities by achieving maximum sDA and minimum ASE by up to 68.8% and 20% in both positions, respectively. Moreover, the centrally positioned square window presents the lowest ASE level of 14.4% among other cases. However, the windows in a higher position, especially horizontal windows obtain the highest values of sDA, UDI, and ASE by up to 77%, 59%, and 30%, respectively. Therefore, the ASE rates deteriorate by increasing the sill height and head height of windows. This paper can provide window design recommendations based on the comparison of dynamic daylight metrics for five common window shapes.

Enhancing visual comfort with Miura-ori-based responsive facade model

With the advancement of technology, buildings are expected to have responsive facades with the potential to adapt themselves according to ever-changing environmental conditions. The paper presents a design for a responsive facade model based on origami principles that aim to enhance visual comfort for building occupants. The model features kinetic elements that reduce solar heat gain while maintaining visual comfort. The design takes into account not only the sun's impact on the façade but also the position of the occupants, which can change over time. To evaluate visual comfort, the study used a simulation model that considers key daylight performance metrics, including Daylight Autonomy, Daylight Glare Probability, Useful Daylight Illumination, Exceeded Useful Daylight Illumination, and visual performance criteria. The simulations were conducted in Istanbul, which has a Mediterranean climate and compared to a base scenario without a facade module. The results showed that the proposed origami-based responsive facade outperforms the base scenario in terms of daylight performance enhancement.

Light exposure in home-based work: Can a simple lighting system increase alertness?

Since the proportion of digital and more flexible work in the western labour market increases, more and more employees are working at least partly from home. This development was even enhanced by the COVID-19-pandemic. In contrast to office workplaces, lighting at home-based workplaces is less studied and regulated. Lighting has been shown to not only ensure vision but also evoke non-image forming effects such as changes in alertness. In this study, light exposure of nine office employees at their home-based workplaces was investigated. Illuminance at home-based workplaces was found to be low, compared to office standards. In addition, melanopic equivalent daylight illuminance (MEDI) did not reach recommendations for healthy daytime light exposure. Furthermore, an additional lighting was installed at participants’ desks in order to examine possible effects on alertness. Mean illuminance and MEDI during work were increased by the additional lighting. A decrease in subjective sleepiness could be shown after 6 hours, although differences were not significant. Improvements of response time in a psychomotor vigilance task were already achieved at the beginning of work and after 3 hours. This study shows that lighting conditions at home-based workplaces often do not meet the criteria for health-promoting lighting in terms of non-image forming effects.

Building energy conservation potentials of semi-transparent CdTe integrated photovoltaic window systems in Bangladesh context

Building integrated photovoltaic systems are getting popular worldwide due to their building energy conservation properties alongside emission-free electricity generation capabilities. BIPV is a suitable way to generate renewable energy without wasting any land or building space. Bangladesh has set a target to generate a great portion of its electricity from solar energy and has already implemented different photovoltaic applications. However, Bangladesh still has no policy and guidelines to implement BIPV technology in its different types of buildings. In this study, we investigated the energy conservation potentials of three different configurations of semi-transparent CdTe combined building integrated window systems in an office building considering Bangladesh's climate conditions. To investigate the building energy conservation potentials of BIPV window systems, an EnergyPlus-based numerical simulation model was developed and validated with outdoor experiment data. The annual energy simulation results indicate that in all climate conditions, CdTe combined BIPV windows can save ranging from around 30–61% of electricity consumption compared to conventional window systems. Besides, it generate around 270 kWh electricity and ensure indoor daylight illuminance level at 300 lux. Moreover, in all climate conditions, south-faced BIPV windows are more efficient for power generation, but east-faced windows are more efficient to reduce net electricity consumption.

Linear regression based indoor daylight illuminance estimation with simple measurements for daylight-linked lighting control

Accurate prediction of indoor daylight illuminance is crucial for daylight-based lighting controls. However, determining the illuminance using physics-based simulation tools requires significant amounts of information, e.g. grid of sensors, sky model, 3D geometry of a target building and surroundings, etc. In this study, the authors suggest a daylight illuminance estimation method with minimal data of two reference sensors and two prior measurements. It is shown that the daylight coefficient and sky luminance distribution can be substituted by the illuminance of the reference points and illuminance of two or more target points at past times. The method was validated on a large open space with north-facing skylight windows and showed an 11.9% mean absolute percentage error. Additionally, a reference point selection method is presented. The proposed method is practical for daylight-based lighting control applications.

Effect of semi-transparent a-Si PV glazing within double-skin façades on visual and energy performances under the UK climate condition

Various studies have assessed the energy performance alterations affected by the novel technology of Building-Integrated Photovoltaic in Double-Skin Facades (BIPV-DSF), while lighting performance tied to the BIPV-DSF has not received much attention. This paper provides numerical modelling to assess the effect of BIPV-DSF on both indoor visual condition and energy consumption for an office module under a typical climate in the United Kingdom. The proposed study was focused on the comparisons between a reference case (a DSF office module with both layers using clear double glazing) and a design case of the same office module with BIPV-DSF using semi-transparent Amorphous Silicon PV glazing. Results show a significant drop in maximum daylight illuminance of 73% by configuring the BIPV-DSF with reference to the regular DSF. It was also reported the resultant average and minimum daylight factors (0.65% and 0.00%) were not able to meet indoor visual comfort requirements for office environments. Furthermore, it was found that the use of BIPV-DSF resulted in a net increase of 8% in building energy consumption over the reference DSF. Therefore, it is concluded that in the present context the BIPV-DSF is not viable for a commercial installation under the UK's climate conditions.

Developing light transmitting concrete for energy saving in buildings

Energy consumption is constantly increasing all around the world, and one of the substantial energy consumption fields is the electricity required for lighting in buildings. There are various approaches to tackle this problem, among which the use of transparent facades is the common method to reduce electrical energy consumption in modern buildings such as museums; However, these solutions have many problems, such as space security, heat gains during summer, and glare; The main problems related to transparent facades are energy loss through light transmitting seams and visual discomfort. Hence, it is necessary to develop a new method that can pass natural light to enhance visual comfort without damaging the thermal insulation of the building's exterior walls. One solution that can be given to this issue is using light transmitting concrete. In this study, five high-performance light transmitting concrete samples, including the different amounts of optical fiber were made, and their performances in terms of daylight and electricity saving have been analyzed based on simulation with Diva for Rhino software. For a better comparison between different studies, the analysis was done based on the reference office, which had been used in previous relevant studies. As a result, the reference office was modeled in 6 cities (Tehran, Houston, Phoenix, San Francisco, Vancouver, & Chicago). It was found that using this material along with using lighting sensors resulted in 45.7%, 31.5%, and 38.8% electricity saving for offices in Tehran, Vancouver, and Phoenix, respectively, and also can increase UDI (Useful Daylight Illuminance) by about 39% in Tehran.

MULTIOBJECTIVE OPTIMIZATION OF THE INTERGENERATIONAL RESIDENTIAL SPACE WITH THE GOAL OF DAYLIGHTING AND THERMAL COMFORT

ABSTRACT (1) Background: An ageing population and two-child policy have led to the transformation of China’s family structure, and multigenerational residences account for an increasing proportion of mainstream family residences. Different generations of residents have great differences in behaviour patterns and health requirements, but existing residential buildings are not especially designed for health needs. (2) Methods: First, based on relevant codes and a questionnaire survey, the spatial needs and behaviour patterns of different generations of residents are obtained, and the benchmark model is established based on the Grasshopper (GH) parametric platform. Then, based on the GH platform and the building simulation plug-in, which are Ladybug Tools and a multiobjective optimization tool named Wallacei, daylight autonomy (DA), useful daylight illuminance (UDI), and the proportion of thermal discomfort hours (PDH) are taken as daylighting and thermal comfort indicators, and the bedroom location, orientation, bay size, depth to bay ratio, window form, window-to-wall ratio, and horizontal shading width are optimized. Finally, the Pareto front is analysed by the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) comprehensive evaluation method, and the optimal solution is compared with existing multigenerational residences in Tianjin. (3) Results: First, the middle room, oriented south or south by east, large bay, small window-to-wall ratio, and bay window can effectively be improved for indoor thermal comfort, while rooms that are oriented south or south by east, small depth bay ratio, large window-to-wall ratio and balcony can effectively be improved for daylighting quality. Second, compared with existing buildings in Tianjin, the DA, UDI, and PDH of the adult bedroom with the ideal solution are increased by 33.7%, 3.5%, and 10.8%, respectively; the DA, UDI, and PDH of the child bedroom with the ideal solution are increased by 15.5%, 4.2%, and 4.9%, respectively; and the DA, UDI, and PDH of the elderly individual bedroom with the ideal solution are increased by 42.7%, 4.9%, and 1.7%, respectively. (4) Conclusions: The optimization scheme is substantially improved for the health of the indoor daylight and thermal environment of existing housing, and it provides a scientific and quantitative decision-making basis for the healthy design of multigenerational residences.

DAYLIGHTING PERFORMANCE OF HIGH SCHOOL LEARNING ENVIRONMENT IN TROPICS

ABSTRACT The quality of the indoor environment, including the lighting conditions, is crucial in classrooms as it directly affects students’ learning performance and productivity. Natural light is the best light source for visual comfort, aesthetics, and energy efficiency. Malaysia is in a tropical region and has abundant daylight availability that could meet the required lighting during the day. However, in Malaysian schools, electric lights are frequently switched on during classes in the daytime; hence, daylighting is not efficiently utilised. This study investigates the daylighting performance in classrooms in a national high school in Penang, Malaysia. Fieldwork was conducted by measuring incident illumination levels inside selected classrooms in the Teluk Kumbar High School. The results show that average illumination levels were between 400 lux to 1000 lux, more than enough in most classrooms because of the relatively large windows with clear glass. The average daylight ratios recorded in the classrooms were between 6.4 and 9.2%, which may result in glare problems. Simulations were conducted using Design-Builder to further evaluate the annual daylighting performance including Daylight Autonomy (DA), Annual Sun Exposure (ASE) and Useful Daylight Illuminance (UDI). Based on the findings, it is recommended to use shading devices or replace the glazing type to improve daylighting performance for visual comfort. Proper design and selection of windows in schools can significantly improve indoor lighting quality for students and reduce solar heat gain.

Color constancy for daylight illumination changes in anomalous trichromats and dichromats.

Color constancy is the perceptual stability of surface colors under temporal changes in the illumination spectrum. The illumination discrimination task (IDT) reveals worse discrimination for "bluer" illumination changes in normal-trichromatic observers (changes towards cooler color temperatures on the daylight chromaticity locus), indicating greater stability of scene colors or better color constancy, compared with illumination changes in other chromatic directions. Here, we compare the performance of individuals with X-linked color-vision deficiencies (CVDs) to normal trichromats on the IDT performed in an immersive setting with a real scene illuminated by spectrally tunable LED lamps. We determine discrimination thresholds for illumination changes relative to a reference illumination (D65) in four chromatic directions, roughly parallel and orthogonal to the daylight locus. We find, using both a standard CIELUV metric and a cone-contrast metric tailored to distinct CVD types, that discrimination thresholds for daylight changes do not differ between normal trichromats and CVD types, including dichromats and anomalous trichromats, but thresholds for atypical illuminations do differ. This result extends a previous report of illumination discrimination ability in dichromats for simulated daylight changes in images. In addition, using the cone-contrast metric to compare thresholds for bluer and yellower daylight changes with those for unnatural redder and greener changes, we suggest that reduced sensitivity to daylight changes is weakly preserved in X-linked CVDs.

Intelligent Parametric Optimization of Building Atrium Design: A Case Study for a Sustainable and Comfortable Environment

Building atrium design is crucial to maintaining a sustainable built environment and providing thermal comfort to occupants. This study proposes a parametric framework to optimize the atrium’s geometry for environmental performance and thermal comfort improvement. It integrates the parametric design, performance simulation, and multi-objective optimization in the Rhino and Grasshopper platform to realize automatic optimization. The atrium’s well index, shape ratio, volume ratio, position index, and inner interface window-to-wall ratio were set as optimized factors. For the optimization objectives, useful daylight illuminance (UDI), energy use intensity (EUI), and the discomfort time percentage (DTP) were chosen as metrics for the measurement of daylighting, energy use efficiency, and thermal comfort, respectively. Moreover, a geometry mapping method is developed; it can turn atrium shape into rectangular profiles. Thus, the framework can apply to general buildings. To validate the effectiveness of the proposed framework, an atrium optimization case study is conducted for a villa in Poland. According to the optimization results, the performance of the compared three objectives are improved by 43.20%, 15.52%, and 3.89%, respectively. The running time for the optimization is about 36 s per solution, which greatly reduce the human and time cost compared to the traditional working method.

Based on ANN and many-objective optimization to improve the performance and economy of village houses in Chinese cold regions

The number of studies considering building performance optimization (BPO) in the building design phase is steadily growing, but many of the existing studies do not consider the applicability of many-objective optimization algorithms when increasing the objective dimensions. This article first compares the NSGA-II, IDBEA, MSOPS-II, and NSGA-III algorithms. Then, the algorithm most suitable for many-objective optimization is combined with Artificial natural network(ANN) and TOPSIS-AHP to complete the optimization of four dimensions of building energy consumption (EC), useful daylight illuminance (UDI), comfort time ratio (CTR) and energy-saving envelope cost (ESEC) for village houses in cold regions of China. The results show that the NSGA-III algorithm performs well in terms of convergence speed, convergence, diversity, and uniformity when solving many-objective problems compared to the other three algorithms. Finally, four optimization strategies were selected using the TOPSIS-AHP method.

Effect of Interior Space and Window Geometry on Daylighting Performance for Terrace Classrooms of Universities in Severe Cold Regions: A Case Study of Shenyang, China

Good daylighting performance positively affects students’ physical and mental health, learning efficiency, and the building’s energy-saving capability. Due to the terrace classroom having ample space, large capacity, the ability to avoid obstructing sight, and the ability to meet various use needs, it is the most important place in university buildings. However, research on the daylighting performance of university terrace classrooms is limited, leading to a lack of quantitative guidance in early design stages. This study aims to explore the effects of interior space and window geometry of terrace classrooms in universities in severe cold regions on daylighting performance. This research took Shenyang as an example; spatial daylight autonomy (sDA300,50%) and useful daylight illuminance (UDI100–2000) were selected as daylighting performance evaluation indices. Based on the Grasshopper parametric platform, the simulation was carried out using Ladybug and Honeybee plugins. Correlation and regression analyses revealed the relationship between interior space and window geometry parameters and the evaluation indices. The results showed the following: window-to-floor ratio (WFR), classroom height (Htc), window height (Hw), window-to-wall ratio (WWR), classroom width (Wtc), and window width (Ww) have positive effects on improving the daylight sufficiency of the terrace classrooms facing each orientation, and the degree of the effect decreases in order. To ensure the overall daylighting performance, the Wtc can be maximized. The width of walls between windows for south-facing and west-facing classrooms should be 0.9 m. The WWR and WFR for south-facing classrooms should be 0.3–0.5 and 0.11–0.14, respectively. The WWR and WFR for north-facing classrooms should be 0.6–0.7 and 0.14–0.20, respectively. Prediction models are established for the sDA300,50% and UDI100–2000 of the terrace classrooms facing each orientation.

Implementing natural ventilation and daylighting strategies for thermal comfort and energy efficiency in office buildings in Burkina Faso

In recent years, efforts to lessen the environmental impact of the building sector have focused more on passive strategies to develop eco-friendly buildings that reduce energy use and improve thermal comfort. To reduce the construction sector’s resource use, particularly in fast-urbanizing sub-Saharan countries, a paradigm shift is needed. Although integrated daylighting and natural ventilation solutions in building design and construction are still under development in sub-Saharan Africa, their scientific contributions to the construction industry are growing. Therefore, the purpose of this research is to investigate natural ventilation and daylighting improvements in Burkina Faso office buildings to maximize thermal comfort and energy efficiency. The country’s meteorological data from 2004 to 2018 was examined for climatic analysis and utilized in Integrated Environmental Solutions Virtual Environment (IESVE) for natural ventilation and daylight simulations and in Design-Builder (DB) for thermal comfort and energy consumption simulations. 4 simulation rounds were conducted in order to determine respectively from round 1 to 4 the effects of building shape, glazing type, window shading type, and window-to-wall ratio on the daylighting and natural ventilation office building model performances. The findings indicated that on a south–north axis orientation, a ”H”-shaped structure with blue-tinted glass, horizontal louvers for shading, and 30% window-to-wall ratio, is the best option. The best overall option reduced annual energy demand, cooling energy demand, and solar gains by 14.9%, 25.3%, and 68.3% respectively. Hourly average airflow increased by 64.8% and 2% in hot and cold seasons respectively. Indoor air temperature decreased by 3.4 °C in the hot season and increased by 0.4 °C in the cold season. The daylighting analysis results demonstrated benefits with measurements that did not reflect too much light, implying reduced glare and discomfort with Useful Daylight Illuminance (500-2500lux): 56%, Spatial Daylight autonomy (50%): 44.7%, Annual Sunlight Exposure: 12%. This research laid the groundwork for a sustainable, bioclimatic office building model in a landlocked developing nation like Burkina Faso by integrating Climate Based Design Modeling (CBDM) and natural ventilation parameters into the design process.

Near-optimal adaptive predictive control model study for roller shades in office spaces

As improved building energy efficiency becomes mandatory, dynamic shading systems are expected to reduce building energy demand because their control mechanisms are increasingly self-adaptable to changes in the environment. Various shading control strategies had been proposed and compared in existing literature, but their energy performance can be further improved with a more comprehensive consideration of environmental changes and indoor demand. This study develops and validates an adaptive predictive control (APC) model for roller shades that combines simulation-based optimization of shading control with machine learning. The model predicts the appropriate position of roller shades based on multiple environmental parameters, minimizing the building energy demand. EnergyPlus and Python provide continuous energy simulation and data processing. Using pre-simulated datasets, machine learning algorithms develop APC models. The study scenario is a typical office space in Guangzhou, China. Quantitative analysis of the simulation results elucidates the effectiveness of the method. The performance of the model was evaluated using historical meteorological data from 2020. The proposed control model was able to achieve nearly optimal energy efficiency, reducing energy demand by 38.3% while reaching annual Useful Daylight Illuminances of 72.9%.

An Analysis of Real-Time Measured Solar Radiation and Daylight and Its Energy Implications for Semi-Transparent Building-Integrated Photovoltaic Façades

For analyzing cooling loads, day-lighting, and building-integrated photovoltaic (BIPV) systems, solar radiation and daylight illuminance data are required. However, these data are sparse. Furthermore, studies have shown that the energy potential of building-integrated photovoltaic (BIPV) systems for the entire building skin (BS) and unconventional orientations, such as east, west, and north need further exploration. Thus, this study presents findings from measured solar data and an energy analysis of semi-transparent BIPV. Firstly, solar radiation and daylight data measured from June 2019 to May 2020 in Hong Kong are presented. The analyzed solar-radiation data were used to determine the solar-energy potential of BIPV for BS and the four principal building orientations (i.e., N, E, S and W). With a simple analytical approach, the solar data’s building-energy implications for semi-transparent BIPV were assessed. The findings showed that the annual average horizontal global-, diffuse-, and direct-irradiance values were 291.8, 164.3, and 127.5 W/m2/day, respectively. Similarly, 120, 72, and 107 klux were obtained as the peak global, diffuse, and direct illuminance, respectively. Furthermore, the results show the potential of using BIPV on the entire BS in Hong Kong. It was also observed that a semi-transparent BIPV façade integrated with daylight-linked lighting controls could offer significant energy savings in electric lighting and cooling while also producing energy. In particular, BIPV façades with a large window-to-wall ratio (WWR) of 80% can provide an overall energy benefit of up to 7126 kWh.

Lighting and visual comfort performance of commercially available tubular daylight devices

Tubular daylight devices (TDDs) require a much smaller roof opening than conventional skylights and, because of their highly reflective tube, they can deliver daylight farther away from the building envelope. This can provide lighting energy savings, increasing resilience in new and existing buildings. Different types and configurations are available amongst commercially available TDDs, including domes/diffusers with varying optical properties and the diameter of the TDD. This paper presents a comprehensive experimental evaluation of the lighting and visual comfort performance of multiple configurations of commercially available TDDs, varying dome type (prismatic and clear), diffuser type (Fresnel and prismatic), and diameter (53 and 35 cm), under a range of environmental conditions (different times of day/year, sky cover). Based on illuminance measurements, estimated lighting energy use is also presented. Results indicate that, for clear sky, light levels increase and energy use decreases with solar altitude (e.g., 16 Wh/m2 daily energy use intensity on a high maximum daily solar altitude (MDSA) day and 34 Wh/m2 on a low MDSA day) and TDD diameter (e.g., 34 Wh/m2 and 69 Wh/m2 for 53 cm and 35 cm TDDs, respectively, for low MDSA). The daily illuminance profile is more rounded for prismatic domes and has higher peaks for clear domes; this translates into a somewhat higher average daily useful daylight illuminance (DUDI) for prismatic domes (86 %) when compared to clear domes (80 %). No clear impact of diffuser type was apparent. Measurements indicated no discomfort glare for any of the conditions tested.